Refining lubricating oils with propane



Jan. 17, 1939. H. O. FORREST ET AL 2,143,872

REF'INING LUBRICA'PING OILS WITH PROPANE Filed Dec. 51, 1936 SURGE MA/K same/sues: mm? 64 6.3

mum/vs mm:

PIPOfiQ/VE 5102965 heavy In verve/s:- Henry 0. FOP/88f ATTORN EY Patented Jan. 17, 1939 alias-l2 PROPANE V I KHenry 0. Forrest, Teaneck, Lee

Wes signers Company, Chicago, IlL,

diana :va nan; to Standard Oil a corporation of Int Application December 31, 19zc,sena1No.-r1a,5ss

Claims. 01. 196-13);

This invention relates to the, refining of lubri cating' oils with propane, and it pertains more particularly to an improved apparatus and method for chilling in the dewaxing} step andimproved methods andapparatus for refining hydrocarbon oils containing resins. In certain propane dewaxing processes we have found that the vapor velocities in the chillers are so great as to cause an undue amount of foaming and entrainment One object of our invention is to provide a new and improved system for chilling propane oil solutions by evaporative cooling in horizontal chillers without losing the advantages that we have heretofore obtained by introducing cold propane onto bubble plates 'in the upper part of the vertical chillers. In other words, our object is to provide a method and means for utilizing the refrigeration value of cold propane and to'simulchilling by contacting. propane vapors leaving the horizontal chiller with refrigerated propane prior to the introduction of the refrigerated propane into said chillers for make-up diluent and 2 refrigerant.

system a new combination of propane refining processes particularly adapted for the treatment of Pennsylvania cylinder stocks or other viscous lubricants which are substantially free from asphalt but which contain waxes and resins. A further object is to provide an improved combination of dewaxing and deresinating steps with an improved propane recovery system which will 3 be more simple and economical than systems heretofore employed. A further object is to provide optimum operating conditions for the refining of Pennsylvania cylinder stocks andsimilar lubricating oil fractions.

In practicing our invention we first heat the stock with propane to a temperature far above that required for complete wax solution, and we then chill the mixture, employing a plurality of horizontal batch chillers. By employing horizontal chillerswe obtain, lower vapor velocities and less foaming and entrainment than we would have in vertical chillers of the same diameter, and we can remove the propane at spaced points alongthe chiller at rates which effect optimum 0 wax crystallization. To cooperate with the horizontal chillers we provide a combination gas washer and trap. The propane from. the chillers is scrubbed with cold propane in the washer, thus warming up the cold propane so that it will not cause shock chilling when added to the oilwhen the 'chillingis effected in vertical towers.

taneously avoid entrainment and prevent shock v A further object is rto provide in an improved propane mixturein the chillers. Propane leaving this scrubberis passed through a trap and thence to the compressor, liquids from the trap being returned for admixture with oil andlpropane prior to the heating step.

We have discovered that for Pennsylvania cylinder stocks or similar oils the optimum feed mix ratio of propane tech is about from 2:1 to 2 1. The warm mix ratio in the chiller is about 2 :1. The cold mix ratio in the chiller is about 3:1.,10 The filtering ratiois about 3:1 and the deresinate ing ratio is about :1. Although it is inherent in a propane dewaxing process that certain resins or colorbodies areremoved from-,the oils with the wax, we have found that it is desirable to include a high temperature deresinating treat ment after the dewaxing step, preferably effect-- ing a fractionation at a temperature of about 180 F. followed by a fractionation or washing of theresins at a temperature of about-150 F. We have found that considerable economies can be effected by increasing the temperatures and pressures which have heretofore been employed in depropanizing the finished oil so that this propane may be liquefied and stored at about 130 F. 2F for use in the deresinating step, this hot propane storage system being operativelyconneoted with the warm propane storage system heretofore employed in dewaxing processes. 4

Our invention will'be more readily understood from the following detailed description of a preferred embodiment and from the accompanying drawing which forms a part of this specification, and which diagrammatically represents a plan partly in elevation, of our improved system.'

We will describe the invention as applied to the refining of a Pennsylvania cylinder stock having a viscosity of about 145 seconds Saybolt at 210 F. and we will describe the operating conditions, quantities and proportions for a plant-40 designed to handle about 1100 barrels/day of such charging stock. It should be understood, howeven'that our'invention is applicable to the refining of any oil stocks from any crude source, provided the necessary adjustments are made in proportions and operating conditions, as will be apparent to those skilled in the art. While we refer to propane as our refining agent, it should be understood that the propane may contain or be replaced by other normallygaseous hydrocarbons, particularly ethane, isobutane and butane, propylenabutylene, etc. 'We prefer to employ a good grade of commercial propane.

About 14,440 pounds/hour of charging stock is introduced through line lllandpump II" for adis passed through heater 1! which raises the temperature of the mixture to about 190 F. We

have found that the filterability of the wax can be markedly improved by this initial heating to a temperature which is far above that required for complete wax solution. Although temperatures as low as 140 to 150 1". may be satisfactory for some stocks, in the present case we advise heating to 190 I". Having superheated the mixture to insure proper wax crystallization, we next chill it in cooler ii to a temperature of about F. by heat exchange with cooling water and then to a temperature of about 70 F. to 100 F. by heat exchange with the dewaxed solution which has previously been used to chill propane, as will hereinafter be described; (to avoid complexity this last heat exchange is not shown in the drawing). The mixture is then introduced into warm solution tank II which is designed to operate at 225 pounds gauge with a warm solution at 100 F. which is preferably maintained in equilibrium with propane storage tanks l2 through line l8.

Warm solution from tank I1 is withdrawn through line i9 into one of the horizontal chillers 20, the chiller having previously been conditioned to avoid shock chilling on the introduction of solution. Chilling is effected batchwise by removing propane vapors from the chiller through line 2| and line 22 to the base of scrubber 23, it being understood, of course, that one chiller is being cooled while another is being emptied, as many chillers as necessary being employed for maintaining continuous operation of the filters.

Cold propane is introduced through line 24 at the top of scrubber 28 and is contacted with the warm propane vapors therein. The condensation of the propane in this scrubber warms up the cold propane to a sufilcient extent to permit its introduction through lines 25 and 25 into chillers 20 for maintaining the desired amount of propane in the chillers at all times, and regulating the cooling rate. Uncondensed propane from the top of scrubber 23 is introduced through line 21 into trap 28 wherein liquids are separated out, and returned through line 29 to be admixed with incoming propane and oil stock. Vapors from trap 28 are led through line 30 and compressor 3| to line 32 and condenser 33, wherein the vapors are liquefied and from which they are returned to propane storage tanks l2.

Slurry from the base of chillers 20 is introduced through line 34 to wax slurry surge tank 35, preferably at a temperature of about 45 F. and with a propane ratio of about 3:1 by volume (14,440 lbs/hour of stock and 24,560 lbs/hour propane). The amount of propane introduced through line 24 in our system is 21,045 lbs/hour, but this amount will necessarily vary with the effectiveness of heat exchange facilities, -insulation, etc.

Slurry is introduced through line 35 by pump 31 to filters 38, the amount of slurry introduced into each filter being controlled by liquid level control valves 39. The filters are preferably of -,the type disclosed in Keith et al. U. 8. Patent 2,050,007.

Wax cake from the filters is withdrawn by screw conveyors and pumps through lines 40 and ll and through heater 42 which heats the mixture to about 180 R, at which temperature it ducted through line 5| is introduced into still 03 which is maintained at about 215 pounds gauge and with a bottom temperature of about 260 F. by steam coils or reboiler 44. Propane from the top of still 43 is. withdrawn through line 45 to line 32. Hot solution from the bottom of still 03 is introduced through line 41 into stripper 48 where it is stripped with steam from line 49, the steam and propane being withdrawn through line 59 to condenser 5|. With the 1970 pounds/hour oi wax (petrolatum), there are 2870 pounds/hour of propane thus introduced into the recovery system, of which propane about 2745 pounds/hour are withdrawn through line and about pounds/hour through line 50. The wax is withdrawn through line 52.

Returning now to the filter system, filtrate is removed through lines 53 and 54 to dewaxed solution surge tank 55 the vapor space of which is connected by line 55 to low pressure gas line 51. The wax slurry surge tank 35 is also connected by line 58, and condenser 5| is connected by line 59, to this same gas line 51 which conducts the gases to trap 60 from which liquids are conto line 29 and gases are compressed by compressor 52 discharging into line 32.

Blow-back and pressurin gas may be supplied to the filter system through line 53, compressor 54 and lines 55 and 55. The filters are also preferably provided with connections for introducing cold wash propane, the cold propane lines being vented to line 5'|, or to line 53.

Dewaxed solution from tank 55 is passed by pump 5'! through line 58 and heat exchanger 59, wherein it is warmed by propane from storage tanks i2 and line 10. It is this cooled propane from line 10 which is introduced through line 24 at. the top of scrubber 23 as hereinabove described.

The dewaxed oil solution, about 12,470 pounds of oil and 24,800 pounds of propane per hour is heated in this exchanger from -40 to about +40 F. and is then further heated, preferably by suitable exchangers H to a temperature of about 145 F. at which temperature it is admixed with about 45,600 pounds/hour of propane in line 12 at about F. The combined solution is heated from F. to about 180 F. in heater 13 and at this temperature is introduced through line 14 into heavy oil settler 15 and is maintained under a pressure of about Thus we have in this settler about 10 volumes of propane per volume of heavy oil, and at the temperature of 180 F. we find that about 11,180 pounds/hour of deresinated oil and 96,000 pounds/hour of propane are withdrawn therefrom through line 15 (including recycled or recovered oil, as hereinafter described). The precipitated resins are withdrawn from the base of settler 15 through line 11 by means of a pump 18 which can be rendered ineffective by line 19 when liquid level controlled valve 80 is closed.

To 2530 pounds/hour of primary resins and 2800 pounds/hour of propane in line 11 we admix about 21,100 pounds/hour of propane from line 8|, the warm mixture being introduced through line 82 into resin settler 83 which is maintained at about F. and 570 pounds gauge. Resins are withdrawn through line 84 to heater 85 which raises the temperature of the 1 90Jpounds of resins and 1400 pounds of propane to.320 F., at which-temperature the mixture is introduced into flash tower 85 operating at 215 pounds gauge and having a bottom tem- 570 pounds gauge.-

perature of 320 The propane from line 88 to lines 45 and 32 about 1350 pounds/hour.

Resins from the bottom of tower 86 are introduced through line 89 into stripper 90 into which steam is introduced through line 9|, finished resins being withdrawn through line 92. Propane and steam from the top of line 89 is introduced through line 93 into line 50.

The propane-oil solution which separates from the resins in se arator 83 may be returned to line H through line 94, or it may be directly introduced to line 16 through line 95. The solution in line 16 is heated by heater 96, which may be a plurality of exchangers, to a temperature of about 160 F., at which temperature it is introduced into still 91 which is maintained at a pressure of 295 pounds gauge with a bottom temperature of 270 F. which is maintained by re-boiler 90. Propane leaving the upper part of fiash tower 01 through line 99 is liquefied in condenser I00 at a temperature of about F., and is stored in hot propane surge tank 10!, this tank being designed to operate up to pressures of 320 pounds gauge. Hot propane from this tank is Withdrawn through line 102 and pump I03 to lines l2 and M for use in the fractionation processes in settlers l5 and 83. Propane from tank l0i may also be passed through line 104 and condenser l05 to propane storage tanks I2, the amount of propane being regulated by liquid level controlled valve E00.

Hot oil from the base of tower 91 is introduced through line illi to low pressure flash tower 908 from which propane is led by line i09to line 5'1. This fiash tower W0 is preferably operated at about 260 F. and about five pounds gauge. The oil is then passed through line 1 ill to stripper ill where it is stripped with steam from line M2, the steam and propane being passed through line M3 to line 50. The finished heavy oil is withdrawn from the base of the stripper through line H4. at a temperature of about 255 F. In the above system about 6850 pounds/hour propane is passed through line 99 to the hot surge tank, about 900 pounds/hour of propane vapor is passed through line I09 to line 51 and about 50 pounds/hour of propane vapor is passed through line l 13 together with steam to the condenser 5|.

Using about 750 pounds/hour of steam in stripper MI, pounds/hour in stripper 48 and 85 pounds/hours in stripper 90 we find it advisable to employ a stripping steam condenser as a heat exchanger to furnish some of the heat for warming up the propane-oil mixture entering the deresinating step, as indicated in dotted lines by exchanger 13a. By this expedient we may 'condense most of the steam so that only about fifteen gallons per minute of water will have to be introduced through line H5 to condense the remaining steam and remove it through line H6 I skilled in the art example of our invention,

to the sewer.

While we have described in detail the preferred it should be understood that certain details have been omitted because of the already complex fiow diagram, but with the proportions and conditions set forth one details hereinabove described except as defined by the following claims which should be construed as broadly as the prior art will permit.

r We claim: 1. In a propane refining system for dewaxing and deresinating, a warm propane storage tank,

can readily practice the invention. We do not limit ourselves to the particular,

for separately removing means for admixing propane therefrom with waxy oil and for dewaxing said waxy oil in propane solution, means for recovering propane from the separated wax and returning said propane to said storage tank, a hot propane surge tank, means for mixing hot propane from said surge tank with dewaxed oil solution, means for deresinating said hot solution at an elevated temperature and pressure, means for recovering propane from said separated resins, means for depropanizing the hot oil solution at a temperature of about 270 F. and a pressure of about 300 pounds gauge, means for condensing the high pressure propane from said depropanizing means and introducing it into said hot propane surge tank at a temperature of about 130 F., means for passing propane from said hot propane surge tank to said propane storage tank and means for further recovering propane from oil discharged from the depropanizer and for returning said recovered propane to said propane storage tank.

2. A process for refining a wax-bearing oil with propane which comprises dissolving said waxbearing oil in propane, introducing said solution into an elongated horizontal chilling zone, removing vapors from the upper part of said chilling zone, countercurrently contacting said removed vapors with cold propane whereby some of the vapors are condensed and any entrained oil is recovered in the cold propane, introducing the cold propane after the scrubbing step into the chilling zone, passing propane vapors from the scrubbing step into a trap -out zone, compressing and condensing propane vapors from the trap-out zone and returning the condensed vapors to the solution step, collecting liquids in the trap-out zone, and separately returning said liquids for admixture with the propane-waxy oil solution.

3. The method of refining substantially asphalt-free-cylinder stock which comprises maintaining a supply of warm propane, mixing said stock with about 2 /2 to 3 volumes of warm propane, from said supply heating the mixture to about to 190 F., cooling the heated mixture to efiect the crystallization of wax in separable form, separating the wax from the propane solution at a low temperature, increasing the propane ratio of the dewaxed oil solution to about 10 volumes of propane per volume of dewaxed oil, heating the mixture to about 150 to 180 F. at a pressure sufiicient to maintain the propane in a liquid state for effecting phase separation of two liquid phases, removing a portion of the propane from one of said phases at a pressure of the order of 300 pounds per square inch, condensing the propane from said propane removal step at a temperature of the order of 130 F., maintaining a supply of this hot propane and using this hot condensed propane for increasing the propane ratio of the dewaxed oil subsequent to the dewaxing step and prior to the high temperature separation step.

4. In apparatus of the class described, a warm propane storage tank, a chill chamber, means for mixing propane from the storage tank with a waxy oil and for introducing said waxy oil propane mixture into said chill chamber, a scrubbing chamber, asource of cold propane, means for passing gases from the chill chamber and cold propane from said .source, respectively, to said scrubbing chamber, means for returning liquid from said scrubbing chamber to said chiller, a

filter, means for transferring chilled propane-oilwax slurry from said chillers to saidrfilter, means oil and mm from said filter, a hot propane storage tank, means for at high temperature, and means for returning adding hot propane from said hot propane storsaid high temperature propane condensate to age tank to the means for removing oil from said said hot propane storage tank.

filter to form a hot mixture of filtrate and pro- 5. The apparatus of claim 4 which includes 5 pane, means for heating the hot mixture to a means for passing propane from the warm protemperature of about 150 to 180 F., means for pane storage tank through a cold filtrate exseparating two liquid phases from the heated changer to provide th s ur e f l pr p mixture, systems for separately depropanizing and to warm up the cold filtrate.

saidseparate liquid phases, means for condensing HENRY O. FORREST. 10 propane from one of said depropanizing systems LEE VAN HORN. 10 

